Airline fees: a big source of irritation for consumers and good joke fodder for comedians. Most newer fees cover services that were formerly included in the price of a ticket, which is annoying, but those services—from handling checked baggage to providing in-flight meals—generate out-of-pocket costs for airlines. Moreover, travelers can choose to avoid paying these fees.

But the most annoying fees are the ones that don't have any rational justification. These include supposedly "optional" fees that, really, are often not optional; fees for actions that benefit airlines; and gouge fees unrelated to any real airline costs. Airlines often waive or reduce these fees for travelers on premium-class or full-fare economy tickets, exalted-level frequent flyers, and travelers using some airline-sponsored credit cards. But ordinary travelers either pay or go without.